Validity and Practical Application of Muscle Oxygenation Monitoring for Identifying Maximal Fat Oxidation in Cyclists

The accurate detection of several physiological milestones, such as maximal fat oxidation (MFO), is an important factor for cycling performance and for programming effective and individualised training. However, the procedure to identify the MFO is often too complex and expensive. Near-infrared spectroscopy (NIRS) technology provides a noninvasive measurement that can be used to detect different physiological variables. The aim of this study was to assess the validity of utilising the muscular oxygen saturation visualisation methodology for the identification of the MFO point in trained cyclists. Twenty-two recreational endurance-trained cyclists (19 men and 3 women; age: 27.9 ± 5.4 years; body mass: 69.7 ± 7.1 kg and VO_2max: 60.3 ± 7.0 mL/kg/min) performed a submaximal and maximal exhaustion test. All the data were collected on a single day. The validity of the visualisation methodology for the maximal fat oxidation point was analysed against a gas analyser. The detection of maximal fat oxidation (MFO) using the methodology and device employed does not appear to accurately specify the precise point at which MFO occurs (bias = 90 ± 218 s and LOA = 429 s). However, our results indicate that it may be a valid technique for identifying the MFO zone; biases were HR = 4.7 ± 11.9 bpm, VO₂ = 1.49 ± 5.7 mL/kg/min and power = 19.5 ± 31.2 W, whereas the concordance coefficients were 0.783, 0.243 and 0.170, respectively. It is not possible to detect MFO using NIRS device. However, it is possible to detect a general zone in which MFO occurs.